We investigated the effects of fertilizer application on the partitioning of gross primary productivity (GPP) between contrasting full-sib clones of Pinus taeda (L.). Our objective was to determine if fertilizer growth responses resulted from similar short-term changes to partitioning. A modeling approach incorporating respiratory carbon (C) fluxes, soil CO2 efflux (FS), and biomass was applied to a factorial design with two clones, fertilizer and control treatments, and four sequential monthly harvests of seedlings planted in a greenhouse. Partitioning was integrated over 121 days to above, belowground, and total net primary production (ANPP + BNPP = NPP), total belowground C flux (TBCF), aboveground plant respiration (APR), and FS. While both clones showed similar GPP and responses to fertilizer application, they did so by partitioning GPP in different ways. Fertilizer application increased GPP and resulted in corresponding increases in ANPP, BNPP, and TBCF (p < 0.01). When considered as a fraction of GPP partitioned, differences between clones emerged. Clone-by-fertilizer interactions for carbon use efficiency (i.e. NPP / GPP), ANPP / GPP, and APR / GPP were all observed (p < 0.10). TBCF was significantly greater in one clone, indicating that plant-soil interactions could be affected by clonespecific partitioning. The other clone had greater growth efficiency (ANPP / GPP) without fertilizer, but with fertilizer application the clones were similar. Our results suggest multiple possible short-term ecophysiological mechanisms are responsible for fertilizer growth response in different yet closely related clones.
Stovall, Jeremy P.; Seiler, John R.; and Fox, Thomas R., "Short-term carbon partitioning fertilizer responses vary among two full-sib loblolly pine clones" (2012). Faculty Publications. 202.